LCD driving circuit using operational amplifier and LCD display apparatus using the same

ABSTRACT

In an operational amplifier includes: a control unit switches an operation mode between first and second operation modes. A first differential stage circuit section differentially-amplifies a first input signal supplied through a first input node in the first operation mode, and a second input signal supplied through the first input node in the second operation mode, similar to a second differential stage circuit section. A first output drive stage circuit section is configured to amplify the first input signal differentially-amplified by the first or second input differential stage circuit section to output as a first drive voltage, similar to a second output drive stage circuit section. First and second power supplies supply voltages in a first voltage range to the first differential stage circuit section and the first output drive stage circuit section in the first operation mode, and to supply voltages in the first voltage range to the second differential stage circuit section and the first output drive stage circuit section in the second operation mode, similar to third and fourth power supplies. The drive voltage on each of the first and second output nodes is fed back.

INCORPORATION BY REFERENCE

This patent application claims a priority on convention based onJapanese Patent Application No. 2009-185451 filed on Aug. 10, 2009. Thedisclosure thereof is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an operational amplifier, a drivingcircuit using the same, for a liquid crystal display apparatus and aliquid crystal display apparatus.

BACKGROUND ART

A recent trend of a thin flat panel is toward more and more increasingin size. In particular, in the field of television, there is a situationwhere even a liquid crystal panel exceeding 100 inches is put into themarket, and it is thought that the trend will never change. However,along with the increase in size of a liquid crystal panel, a data lineload of a TFT LCD (Thin Film Transistor Liquid Crystal Display) becomesincreasingly large, and therefore power consumed in an amplifier of anLCD driver that drives the TFT LCD tends to increase. Further, in orderto reduce the number of LCD drivers to be used, the number of outputs ofone chip tends to increase more and more. That is, a power consumptionamount by one chip increases more and more. As a result, the powerconsumption amount as a whole of LCD drivers increases, and thereby achip temperature abnormally rises.

Among measure for the temperature rising of a chip, one having beenrecently focused on is a method that reduces power consumed by a chip.In this method, a voltage V_(DD)/2 that is a half of a power supplyvoltage V_(DD) is supplied to the chip, and an amplifier operates in thevoltage V_(DD)/2.

However, as this method becomes widespread, there arise variouscircuit-based problems. For example, there is a problem that, in thecase of a conventional circuit, if only a differential stage is operatedin the range of V_(SS) (GND) to V_(DD), and an output stage is operatedwith the V_(DD)/2 power supply, a voltage balance cannot be maintainedon the circuit operation, and therefore a desired characteristic cannotbe obtained.

In conjunction with the above, Patent literature 1 (JP 2002-175052A)discloses an operational amplifier. The operational amplifier isintended to reduce a power consumption amount. In the following,referring to FIGS. 1 to 3, the conventional operational amplifier in thePatent literature 1 will be described.

FIG. 1 is a circuit diagram showing a configuration of the conventionaloperational amplifier circuit in the Patent literature 1. Theconventional operational amplifier circuit is provided with twodifferential type input stage circuits 140 and 240, two drive stagecircuits 130 and 230, four switch circuits 30, 40, 50, and 60, twoP-channel MOS transistors MP180 and MP280 and two N-channel MOStransistors MN180 and MN280. It should be noted that each of the twodifferential type input stage circuits 140 and 240 and two drive stagecircuits 130 and 230 is supplied with a power supply voltage (V_(DD))and a power supply voltage (V_(SS)).

The drive stage circuit 130 is connected to an output terminal 110through drains of the P-channel MOS transistor MP180 and the N-channelMOS transistor MN180. Similarly, the drive stage circuit 230 isconnected to an output terminal 210 through drains of the P-channel MOStransistor MP280 and the N-channel MOS transistor MN280. A source of theP-channel MOS transistor MP180 is supplied with the power supply voltageV_(DD). A source of the N-channel MOS transistor MN180 is supplied witha half (V_(DD)/2) of the power supply voltage V_(DD). Also, a source ofthe P-channel MOS transistor MP280 is supplied with a half (V_(DD)/2) ofthe power supply voltage V_(DD). A source of the N-channel MOStransistor MN280 is supplied with the power supply voltage V_(SS).

The switch circuit 30 is provided with switches SW301 to SW304, andcontrols connections between output terminals 110 and 210 andodd-numbered and even-numbered terminals 310 and 320. The switch circuit40 is provided with switches SW401 to SW404, and controls connectionsbetween terminals 410 and 420 and input terminals 120 and 220 of thedifferential type input stage circuits 140 and 240. It should be notedthat the terminal 410 is supplied with a voltage INP from apositive-side DAC (digital analog converter), and the terminal 420 issupplied with a voltage INN from a negative-side DAC. The switch circuit50 is provided with four switches SW501 to SW504, and controlsconnections between the differential type input stage circuits 140 and240 and the drive stage circuits 130 and 230. The switch circuit 60 isprovided with four switches SW601 to SW604, and controls connectionsbetween the output terminals 110 and 210 and input terminals 121 and 221of the differential type input stage circuits 140 and 240.

The conventional operational amplifier circuit can use the switchcircuits 30 to 60 to change a configuration of an amplifier circuit thatdrives the odd-numbered and even-numbered terminals 310 and 320.Specifically, in a pattern 1, the eight switches SW301, SW303, SW401,SW403, SW501, SW503, SW601, and SW603 are in an ON state, and the eightswitches SW302, SW304, SW402, SW404, SW502, SW504, SW602, and SW604 arein an OFF state, and the pattern 1 and a pattern 2 opposite to thepattern 1 are switched to each other.

In the case of the pattern 1, the voltage INP is supplied from thepositive-side DAC to an amplifier circuit including the differentialtype input stage circuit 140 and the drive stage circuit 130. Also, anoutput is outputted from the output terminal 110 to the odd-numberedterminal 310 as an odd-numbered output Vodd. At this time, the voltageINN is supplied from the negative-side DAC to an amplifier circuitincluding the differential type input stage circuit 240 and the drivestage circuit 230. Also, an output is outputted from the output terminal210 to the even-numbered terminal 320 as an even-numbered output Veven.

On the other hand, in the case of the pattern 2, the voltage INP issupplied from the positive-side DAC to an amplifier circuit includingthe differential type input stage circuit 240 and the drive stagecircuit 130. Also, an output is outputted from the output terminal 110to the even-numbered terminal 320 as the even-numbered output Veven. Atthis time, the voltage INN is supplied from the negative-side DAC to anamplifier circuit including the differential type input stage circuit140 and the drive stage circuit 230. Also, an output is outputted fromthe output terminal 210 to the odd-numbered terminal 310 as theodd-numbered output Vodd.

The conventional operational amplifier circuit operates as follows, todrive capacitive loads connected to the odd-numbered and even-numberedterminals 310 and 320. At this time, the differential type input stagecircuits 140 and 240 and the drive stage circuits 130 and 230 operate ina voltage range of the positive power supply voltage V_(DD) to thenegative power supply voltage V_(SS). Also, the MOS transistors MP180and MN180 and the MOS transistors MP280 and MN280 are outputtransistors, and respectively operate in voltage ranges of V_(DD) toV_(DD)/2 and V_(DD)/2 to V_(SS). This results in the power consumptionamount consumed in an output stage to be approximately halved.

FIG. 2 is a circuit showing a configuration of the differential typeinput stage circuit 140 shown in Patent literature 1. The differentialtype input stage circuit 140 is provided with six P-channel MOStransistors MP101, MP102, MP103, MP104, MP105, and MP106, and fourN-channel MOS transistors MN101, MN102, MN103, and MN104. It should benoted that sources of the four P-channel MOS transistors MP103, MP104,MP105, and MP106 are connected with the positive power supply voltageV_(DD). Sources of the two N-channel MOS transistors MN103 and MN104 areconnected with the negative power supply voltage V_(SS). Sources of thetwo N-channel MOS transistors MN101 and MN102 are connected to the powersupply voltage V_(SS) through a constant current source I101. Sources ofthe two P-channel MOS transistors MP101 and MP102 are connected to thepower supply voltage V_(DD) through a constant current source I102.

The two P-channel MOS transistors MP101 and MP102 constitutes adifferential pair. The two N-channel MOS transistors MN103 and MN104constitute an active load for the differential pair.

Also, the two N-channel MOS transistors MN101 and MN102 constitutes adifferential pair. The two P-channel MOS transistors MP103 and MP104 andthe two P-channel MOS transistors MP105 and MP106 respectivelyconstitute current mirror circuits. Outputs of the current mirrorcircuits are connected to drains of the two N-channel MOS transistorsMN103 and MN104.

Further, the input terminal 120 is connected to respective gates of theN-channel MOS transistor MN101 and the P-channel MOS transistor MP102.The input terminal 121 is connected to respective gates of the N-channelMOS transistor MN102 and the P-channel MOS transistor MP101.

Also, respective drains of the N-channel MOS transistor MN104 and theP-channel MOS transistor MP106 are connected to the two switches SW501and SW502 through a terminal 123.

Based on such a configuration, differential input signals supplied tothe input terminals 120 and 121 are subjected to conversion, and thenoutputted from the terminal 123.

A configuration and an operation of the differential type input circuit240 are the same as those described above. However, it should be notedthat the two input terminals 120 and 121, a terminal 123, and twoswitches SW501 and SW502 should be replaced by the two input terminals220 and 221, a terminal 223, and switches SW503 and SW504, respectively.

FIG. 3 is a circuit showing a configuration of the conventional drivestage circuit 130. The drive stage circuit 130 is provided with threeP-channel MOS transistors MP107 to MP109, an N-channel MOS transistorMN105, a P-channel MOS transistor MP110, and two constant currentsources 103 and 104. It should be noted that a source of each of thethree P-channel MOS transistors MP107 to MP109 is supplied with thepower supply voltage V_(DD). A source of the N-channel MOS transistorMN105 is supplied with the power supply voltage V_(SS). Each of the twoconstant current sources 103 and 104 is supplied with the power supplyvoltage V_(SS).

A gate of the N-channel MOS transistor MN105 is connected to the twoswitches SW501 and SW502 through a terminal 131. A drain of theN-channel MOS transistor MN105 is connected to a drain of the P-channelMOS transistor MP107.

The P-channel MOS transistor MP107 constitutes a current mirror circuitwith each of the P-channel MOS transistors MP108 and MP109. A drain ofthe P-channel MOS transistor MP108 is connected to the constant currentsource 103 through the P-channel MOS transistor MP110. A gate of theP-channel MOS transistor MP110 is connected to a gate of the P-channelMOS transistor MP180. A drain of the P-channel MOS transistor MP109 isconnected to a gate of the N-channel MOS transistor MN180 and theconstant current source 104.

According to such a configuration, in the drive stage circuit 130, aninput voltage supplied from the terminal 131 is received by theN-channel MOS transistor MN105, of which output drives the P-channel MOStransistor MP180 and the N-channel MOS transistor MN180. That is, acomposite output signal according to an input signal from the terminal131 is outputted from the terminal 110.

The drive stage circuit 230 also has the same configuration andoperation. However, it should be noted that the P-channel MOS transistorMP280, the N-channel MOS transistor MN280, the terminal 132, and twoswitches SW501 and SW503 should be replaced by the P-channel MOStransistor MP280, the N-channel MOS transistor MN280, the terminal 231,and two switches SW502 and SW504, respectively.

CITATION LIST

-   [Patent literature 1]: JP 2002-175052A

SUMMARY OF THE INVENTION

In the above-described conventional example, it is very difficult toconfigure an interface with a circuit having a so-called combineddifferential stage including typical P-channel and N-channeldifferential stages. This problem occurs because an interface betweenthe differential stage and the output stage is configured only on thebasis of one system.

Referring to FIGS. 1 and 3, attention is focused on the two differentialtype input stage circuits 140 and 240. Between the case where adifferential pair including the two NMOS transistors MN101 and MN102operates and the case where a differential pair including the two PMOStransistors MP101 and MP102 operates, the number of transistors in acurrent path is different. For this reason, symmetry of outputcharacteristics between the two drive stage circuits 130 and 230 islost.

It should be noted that the symmetry of output characteristics isdefined as follows. That is, if a difference between a rising time and afalling time of an output pulse is small, it is defined that thesymmetry is good. On the other hand, if the difference between therising time and the falling time is large, it is defined that thesymmetry is poor.

For example, in FIG. 1, a rising time Tr1 and a falling time Tf1 of apulse in an output signal OUTP outputted from the odd-numbered terminal310 (or even-numbered terminal 320) exhibit different values. If anoutput signal having such an asymmetric pulse shape drives a capacitiveload such as a liquid crystal display apparatus, charging/dischargingcharacteristics to/from the capacitive load are degraded. This sort ofoperational amplifier circuit may not meet specifications of an LCDdriver.

In an aspect of the present invention, an operational amplifierincludes: a control unit configured to switch an operation mode betweenfirst and second operation modes; an input section configured to receiveinput signals and supply one of the input signals as a first inputsignal to a first input node in the first operation mode and to a secondinput node in the second operation mode and the other of the inputsignals as a second input signal to the first input node in the secondoperation mode and to the second input node in the first operation mode;a first differential stage circuit section configured todifferentially-amplify the first input signal supplied through the firstinput node in the first operation mode, and the second input signalsupplied through the first input node in the second operation mode; asecond differential stage circuit section configured todifferentially-amplify the second input signal supplied through thesecond input node in the first operation mode, and the first inputsignal supplied through the second input node in the second operationmode; a first output drive stage circuit section configured to amplifythe first input signal differentially-amplified by the first or secondinput differential stage circuit section to output as a first drivevoltage; a second output drive stage circuit section configured toamplify the second input signal differentially-amplified by the first orsecond input differential stage circuit sections to output as a seconddrive voltage; an output section configured to output through a firstoutput node, the first drive voltage in the first operation mode and thesecond drive voltage in the second operation mode, and to output througha second output node, the second drive voltage in the first operationmode and the first drive voltage in the second operation mode; first andsecond power supplies configured to supply voltages in a first voltagerange to the first differential stage circuit section and the firstoutput drive stage circuit section in the first operation mode, and tosupply voltages in the first voltage range to the second differentialstage circuit section and the first output drive stage circuit sectionin the second operation mode; and third and fourth power suppliesconfigured to supply voltages in a second voltage range which isdifferent from the first voltage range, to the second differential stagecircuit section and the second output drive stage circuit section in thefirst operation mode, and to supply voltages in the second voltage rangein the first differential stage circuit section and the second outputdrive stage circuit section in the second operation mode. The first orsecond drive voltage on the first output node is fed back to the firstdifferential stage circuit section from one of the first and secondoutput drive stage circuit sections, and the first or second drivevoltage on the second output node is fed back to the second differentialstage circuit section from the other of the first and the second outputdrive stage circuit section.

In another aspect of the present invention, a driving circuit for aliquid crystal display apparatus, includes: a plurality of operationalamplifiers.

In still another aspect of the present invention, a method of anoperational amplification, is achieved by (a) switching an operationmode between first and a second operation mode; by (b) supplyingvoltages in a first voltage range by first and second power supplies toa first input differential stage circuit section and a first outputdrive stage circuit section, and voltage in a second voltage range,which is different from the first voltage range, by third and fourthpower supplies to a second input differential stage circuit section anda second output drive stage circuit section, in the first operationmode; by (c) supplying voltages in the first voltage range to the secondinput differential stage circuit section and the first output drivestage circuit section, and voltages in the second voltage range to thefirst input differential stage circuit section and the second outputdrive stage circuit section in the second operation mode; by (d)inputting first and second input signals; by (e) supplying voltages inthe first voltage range to the first input differential stage circuitsection and the first output drive stage circuit section, and voltagesin the second voltage range to the second input differential stagecircuit section and the second output drive stage circuit section, inthe first operation mode; by (f) supplying voltages in the first voltagerange to the second input differential stage circuit section and thefirst output drive stage circuit section, and voltages in the secondvoltage range to the first input differential stage circuit section andthe second output drive stage circuit section, in the second operationmode; by (g) differentially-amplifying the first input signal by thefirst input differential stage circuit section, and the second inputsignal by the second input differential stage circuit section, in thefirst operation mode; by (h) differentially-amplifying the second inputsignal by the first input differential stage circuit section and thefirst input signal by the second input differential stage circuitsection, in the second operation mode; by (i) amplifying the first inputsignal differentially-amplified in the (g) or (h), by the first outputdrive stage circuit section; by (j) amplifying the second input signaldifferentially-amplified in the (g) or (h), by the second output drivestage circuit section; by (k) outputting the first and second drivevoltages obtained in the (i) or (j) from the first and second outputsections in the first operation mode, respectively; by (l) outputtingthe first and second drive voltages obtained in the (i) or (j) from thesecond and first output sections in the second operation mode,respectively; by (m) feeding back one of the first and second drivevoltages outputted from the first output section in the (k) or (l) tothe first input differential stage circuit section; and by (n) feedingback the other of the first and second drive voltages outputted from thesecond output section in the (k) or (l) to the second input differentialstage circuit section.

According to the present invention, two input differential stagecircuits and the two output drive stage circuits are respectivelysupplied with voltages from the two power supply voltages having adifferent voltage range. The voltage ranges of the two power supplyvoltages are configured such that a summation of the voltage range canmeet a voltage range necessary for an output operation of a subsequentstage circuit. As a result, a supply voltage can be reduced, and a fulloutput operation of the subsequent stage circuit can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will be more apparent from the following description ofcertain embodiments taken in conjunction with the accompanying drawings,in which:

FIG. 1 is a circuit showing a configuration of an operational amplifiercircuit shown in Patent literature 1;

FIG. 2 is a circuit showing a configuration of a differential type inputstage circuit of the operational amplifier shown in FIG. 1;

FIG. 3 is a circuit showing a configuration of a drive stage circuitdescribed of the operational amplifier shown in FIG. 1;

FIG. 4 is a circuit showing a configuration of an operational amplifieraccording to a first embodiment of the present invention;

FIGS. 5A and 5B are a circuit diagram showing a configuration of anoperational amplifier circuit section in the operational amplifieraccording to the first embodiment of the present invention;

FIGS. 6A and 6B are a circuit diagram showing a configuration of anoperational amplifier circuit section in the operational amplifieraccording to a second embodiment of the present invention;

FIG. 7A-1 is a circuit diagram schematically illustrating a make typeswitch circuit section;

FIG. 7A-2 is a circuit diagram showing the make type switch circuitsection of an N-channel MOS transistor;

FIG. 7A-3 is a circuit diagram showing the make type switch circuitsection of a P-channel MOS transistor;

FIG. 7A-4 is a circuit diagram for realizing the make type switchcircuit section of two types of MOS transistors;

FIG. 7B-1 is a circuit diagram schematically illustrating a transferswitch circuit section;

FIG. 7B-2 is a circuit diagram showing the transfer switch circuitsection of N-channel MOS transistors;

FIG. 7B-3 is a circuit diagram showing the transfer switch circuitsection of P-channel MOS transistors; and

FIG. 7B-4 is a circuit diagram showing the transfer switch circuitsection with two types of MOS transistors.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a liquid crystal display (LCD) driving circuit including anoperational amplifier according to the present invention, and a liquidcrystal display apparatus driven by the LCD driving circuit will bedescribed with reference to the attached drawings.

First Embodiment

FIG. 4 is a circuit showing a configuration of the operational amplifieraccording to a first embodiment of the present invention. Referring toFIG. 4, the operational amplifier according to the present embodimentwill be described. The operational amplifier according to the presentembodiment is provided with an input switching circuit section 70, anoperational amplifier circuit section 80, and an output switchingcircuit section 90.

The input switching circuit section 70 is provided with first and secondinput nodes 71 and 72, first and second input transfer switch circuitsections SW11 and SW12, and first and second output nodes 73 and 74.

The operational amplifier circuit section 80 is provided with first andsecond input nodes 801 and 802, first and second input differentialstage circuit sections 810 and 820, first and second output drive stagecircuit sections 830 and 840, first to fourth power supply voltagesV_(DD), V_(ML), V_(MH), and V_(SS), first and second output nodes 803and 804, and first to tenth transfer switch circuit sections SW1 toSW10. It should be noted that voltages supplied from the power supplyvoltages V_(ML) and V_(MH) are both around a half of the voltagesupplied from the power supply voltage V_(DD). The first output drivestage circuit section 830 is a positive only output stage which outputsa voltage of in a voltage range of V_(DD) to V_(ML), whereas the secondoutput drive stage circuit section 840 is a negative only output stagewhich outputs a voltage of V_(MH) to V_(SS).

The first input differential stage circuit section 810 is provided withfirst and second input nodes 811 and 812, first and second output nodes813 and 814, a positive voltage input node 815, and a negative voltageinput node 816. It should be noted that the first input node 811 is anon-inversion input node, and the second input node 812 is an inversioninput node. The second input differential stage circuit section 820 isprovided with first and second input nodes 821 and 822, first and secondoutput nodes 823 and 824, a positive voltage input node 825, and anegative voltage input node 826. It should be noted that the first inputnode 821 is a non-inversion input node, and the second input node 822 isan inversion input section.

The first output drive stage circuit section 830 is provided with firstand second input nodes 831 and 832, an output node 833, a positivevoltage input node 834, and a negative voltage input node 835. Thesecond output drive stage circuit section 840 is provided with first andsecond input nodes 841 and 842, an output node 843, a positive voltageinput node 844, and a negative voltage input node 845.

The output switching circuit section 90 is provided with first andsecond input nodes 901 and 902, thirteenth and fourteenth transferswitch circuit sections SW13 and SW14, and first and second output nodes903 and 904. The first and second output nodes 903 and 904 arerespectively in charge of odd-numbered output and even-numbered output,which are to be described later. It should be noted that the combinationof the outputs may be switched.

Each of the first to fourteenth transfer switch circuit sections SW1 toSW14 is provided with a common terminal, a first terminal, and a secondterminal. Also, each of the first to fourteenth transfer switch circuitsections SW1 to SW14 has a first state and a second state. In each ofthe first to fourteenth transfer switch circuit sections SW1 to SW14 inthe first state, the common terminal and the first terminal are madeconductive to each other, whereas the common terminal and the secondterminal are insulated from each other. On the other hand, in each ofthe first to fourteenth transfer switch circuit sections SW1 to SW14 inthe second state, the common terminal and the first terminal areinsulated from each other, whereas the common terminal and the secondterminal are made conductive to each other. It should be noted that, inFIG. 4, the first to fourteenth transfer switch circuit sections SW1 toSW14 are represented as being in the first state. In the following, thefirst terminal and the second terminal of each of the first tofourteenth transfer switch circuit sections SW1 to SW14 are respectivelydescribed as a break terminal and a make terminal.

Here, connection relation between the components of the operationalamplifier according to the present embodiment will be described.

The first input node 71 of the input switching circuit section 70 isconnected to a positive DAC (Digital to Analog Converter) (not shown).The first input node 71 of the input switching circuit section 70 isfurther connected to the common terminal of the eleventh transfer switchSW11. The break terminal of the eleventh transfer switch SW11 isconnected to the first output node 73 of the input switching circuitsection 70. The make terminal of the eleventh transfer switch SW 11 isconnected to the second output node 74 of the input switching circuitsection 70.

The second input node 72 of the input switching circuit section 70 isconnected to a negative DAC (not shown). The second input node 72 of theinput switching circuit section 70 is further connected to the commonterminal of the twelfth transfer switch SW12. The make terminal of thetwelfth transfer switch SW12 is connected to the first output node 73 ofthe input switching circuit section 70. The break terminal of theeleventh transfer switch SW 11 is connected to the second output node 74of the input switching circuit section 70.

The first and second output nodes 71 and 72 in the input switchingcircuit section 70 are respectively connected to the first and secondinput nodes 801 and 802 in the operational amplifier circuit section 80.

The first input nodes 801 and 802 in the operational amplifier circuitsection 80 are connected to the first input node 811 of the first inputdifferential stage circuit section 810 and the first input node 821 ofthe second input differential stage circuit section 820.

The first output node 813 of the first input differential stage circuitsection 810 is connected to the common terminal of the second transferswitch circuit section SW2. The second output node 814 of the firstinput differential stage circuit section 810 is connected to the commonterminal of the third transfer switch circuit section SW3. The firstoutput node 823 of the second input differential stage circuit section820 is connected to the common terminal of the sixth transfer switchcircuit section SW6. The second output node 824 of the second inputdifferential stage circuit section 820 is connected to the commonterminal of the seventh transfer switch circuit section SW7.

The voltage input node 815 of the first input differential stage circuitsection 810 is connected to the common terminal of the first transferswitch circuit section SW1. The voltage input node 816 of the firstinput differential stage circuit section 810 is connected to the commonterminal of the fourth transfer switch circuit section SW4. The voltageinput node 825 of the second input differential stage circuit section820 is connected to the common terminal of the fifth transfer switchcircuit section SW5. The voltage input node 826 of the second inputdifferential stage circuit section 820 is connected to the commonterminal of the eighth transfer switch circuit section SW8.

The second input section of the first input differential stage circuitsection 810 is connected with the common terminal of the ninth transferswitch circuit section SW9. The second input section of the second inputdifferential stage circuit section 820 is connected with the commonterminal of the tenth transfer switch circuit section SW10.

A first input node 831 of the first output drive stage circuit section830 is connected to the break terminal of the second transfer switchcircuit section SW2 and the make terminal of the sixth transfer switchcircuit section SW6. A second input node 832 of the first output drivestage circuit section 830 is connected to the break terminal of thethird transfer switch circuit section SW3 and the make terminal of theseventh transfer switch circuit section SW7. A first input node 841 ofthe second output drive stage circuit section 840 is connected to thebreak terminal of the sixth transfer switch circuit section SW6 and themake terminal of the second transfer switch circuit section SW2. Asecond input node 842 of the second output drive stage circuit section840 is connected to the break terminal of the seventh transfer switchcircuit section SW7 and the make terminal of the third transfer switchcircuit section SW3.

An output node 833 of the first output drive stage circuit section 830is connected to the first output node 803 of the operational amplifiercircuit section 80, the break terminal of the ninth transfer switchcircuit section SW9, and the make terminal of the tenth transfer switchcircuit section SW10. An output node 843 of the second output drivestage circuit section 840 is connected to the second output node 804 ofthe operational amplifier circuit section 80, the break terminal of thetenth transfer switch circuit section SW10, and the make terminal of theninth transfer switch circuit section SW9.

The voltage input node 834 of the first output drive stage circuitsection 830 is connected to the first power supply voltage V_(DD), thebreak terminal of the first transfer switch circuit section SW1, and themake terminal of the fifth transfer switch circuit section SW5. Thevoltage input node 835 of the first output drive stage circuit section830 is connected to the second power supply V_(ML), the break terminalof the fourth transfer switch circuit section SW4, and the make terminalof the eighth transfer switch circuit section SW8. The voltage inputnode 844 of the second output drive stage circuit section 840 isconnected to the third power supply V_(MH), the break terminal of thefifth transfer switch circuit section SW5, and the make terminal of thefirst transfer switch circuit section SW1. The voltage input node 845 ofthe second output drive stage circuit section 840 is connected to thefourth power supply V_(SS), the break terminal of the eighth transferswitch circuit section SW8, and the make terminal of the fourth transferswitch circuit section SW4.

The first output node 803 of the operational amplifier circuit section80 is connected to the first input node 901 of the output switchingcircuit section 90. The second output node 804 of the operationalamplifier circuit section 80 is connected to the second input node 902of the output switching circuit section 90.

The first input node 901 of the output switching circuit section 90 isconnected to the common terminal of the thirteenth transfer switchcircuit section SW13. The second input node 902 of the output switchingcircuit section 90 is connected to the common terminal of the fourteenthtransfer switch circuit section SW14. The break terminal of thethirteenth transfer switch circuit section SW13 and the make terminal ofthe fourteenth transfer switch circuit section SW14 are connected to thefirst output node 903 of the output switching circuit section 90. Themake terminal of the thirteenth transfer switch circuit section SW13 andthe break terminal of the fourteenth transfer switch circuit sectionSW14 are connected to the second output node 904 of the output switchingcircuit section 90.

Here, the LCD driving circuit according to the present invention will bedescribed. The LCD driving circuit according to the present invention isprovided with a plurality of the operational amplifiers according to thepresent embodiment.

In general, in a liquid crystal display apparatus, a plurality of liquidcrystal cells are arranged in a matrix. Also, in general, the LCDdriving circuit controls the plurality of liquid crystal cells in unitsof rows or columns. Accordingly, the plurality of operational amplifiersin the LCD driving circuit according to the present invention areconnected in parallel.

Further, the LCD driving circuit according to the present inventioncontrols the plurality of liquid crystal cells in units of two rows ortwo columns. It is preferable for the control to alternatively applypositive and negative voltages to liquid crystal cells in two rows orcolumns.

Next, an operation of the operational amplifier according to the presentembodiment will be described.

First, an operation common to the first to fourteenth transfer switchcircuit sections SW1 to SW14 will be described. Each of the transferswitch circuit sections has the two states. That is, each of thetransfer switch circuit sections transits between the first state thatthe common terminal is made conductive to the first terminal andinsulated from the second terminal and the second state that the commonterminal is made conductive to the second terminal and insulated fromthe first terminal. It should be noted that, preferably, the operationalamplifier according to the present embodiment is further provided with acontrol circuit section (not shown), and the control circuit sectioncontrols states of the first to fourteenth transfer switch circuitsections SW1 to SW14.

Next, in the entire operational amplifier, all the first to fourteenthtransfer switch circuit sections SW1 to SW14 are in either the firststate or the second state. That is, even as the operational amplifier,the transition between the two states is made. It should be noted thatFIG. 4 illustrates the operational amplifier in the first state.

In the operational amplifier in the first state, the first inputdifferential stage circuit section 810 and the first output drive stagecircuit section 830 operate as an operational amplifier. In this case, asignal from the positive DAC (not shown) is outputted to an odd-numberedoutput node.

First, the signal supplied from the positive DAC (not shown) to thefirst input node 71 in the input switching circuit section 70 istransferred to the first input node 811 of the first input differentialstage circuit section 810 through the eleventh transfer switch circuitsection SW11. At this time, the first and second output nodes 813 and814 of the first input differential stage circuit section 810 areconnected to the first and second input nodes 831 and 832 in the firstoutput drive stage circuit section 830 through the second and thirdtransfer switch circuit sections SW2 and SW3, respectively. Also, atthis time, the output node 833 of the first output drive stage circuitsection 830 is connected to the first output node 903 of the outputswitching circuit section 90 through the thirteenth transfer switchcircuit section SW13.

Also, the output node 833 of the first output drive stage circuitsection 830 is connected to the second input node 812 of the first inputdifferential stage circuit section 810 through the ninth transfer switchcircuit section SW9. Accordingly, the first input differential stagecircuit section 810 and the first output drive stage circuit section 830operate as a voltage follower circuit. Here, supposing that an inputvoltage of the first input section of the first input differential stagecircuit section 810 is denoted by Vin, and an output voltage of theoutput section of the first output drive stage circuit section 830 isdenoted by Vout,Vin=Vout.

Further, the voltage input nodes 815 and 816 of the first inputdifferential stage circuit section 810 are connected with first andsecond power supply voltages V_(DD) and V_(ML) through the first andfourth transfer switch circuit sections SW1 and SW4, respectively.

In the operational amplifier in the first state, simultaneously with theabove, the second input differential stage circuit section 820 and thesecond output drive stage circuit section 840 operate as an operationalamplifier. In this case, a signal from the negative DAC (not shown) isoutputted to an even-numbered output node.

First, the signal supplied from the negative DAC (not shown) to thesecond input node 72 of the input switching circuit section 70 istransferred to the first input node 821 of the second input differentialstage circuit section 820 through the twelfth transfer switch circuitsection SW12. At this time, the first and second output nodes 823 and824 of the second input differential stage circuit section 820 areconnected to the first and second input nodes 841 and 842 in the secondoutput drive stage circuit section 840 through the sixth and seventhtransfer switch circuit sections SW6 and SW7, respectively. Also, atthis time, the output node 843 of the second output drive stage circuitsection 840 is connected to the second output node 904 of the outputswitching circuit section 90 through the fourteenth transfer switchcircuit section SW14.

Also, the output node 843 of the second output drive stage circuitsection 840 is further connected to the second input node 822 of thesecond input differential stage circuit section 820 through the tenthtransfer switch circuit section SW10. Accordingly, the second inputdifferential stage circuit section 820 and the second output drive stagecircuit section 840 operate as a voltage follower circuit. Here,supposing that an input voltage of the first input section of the secondinput differential stage circuit section 820 is denoted by Vin, and anoutput voltage of the output section of the second output drive stagecircuit section 840 is denoted by Vout,Vin=Vout.

Further, the voltage input nodes 825 and 826 in the second inputdifferential stage circuit section 820 are connected with third andfourth power supply voltages V_(MH) and V_(SS) through the fifth andeighth transfer switch circuit sections SW5 and SW8, respectively.

In the operational amplifier in the second state, the second inputdifferential stage circuit section 820 and the first output drive stagecircuit section 830 operate as an operational amplifier. In this case,the signal from the positive DAC (not shown) is outputted to theeven-numbered output terminal.

First, the signal supplied from the positive DAC (not shown) to thefirst input node 71 of the input switching circuit section 70 issupplied to the first input node 821 of the second input differentialstage circuit section 820 through the eleventh transfer switch circuitsection SW11. At this time, the first and second output nodes 823 and824 of the second input differential stage circuit section 820 areconnected to the first and second input nodes 831 and 832 in the firstoutput drive stage circuit section 830 through the sixth and seventhtransfer switch circuit sections SW6 and SW7, respectively. Also, atthis time, the output node 833 of the first output drive stage circuitsection 830 is connected to the second output node 904 of the outputswitching circuit section 90 through the thirteenth transfer switchcircuit section SW13.

Also, the output node 833 of the first output drive stage circuitsection 830 is connected to the second input node 822 of the secondinput differential stage circuit section 820 through the tenth transferswitch circuit section SW10. Accordingly, the second input differentialstage circuit section 820 and the first output drive stage circuitsection 830 operate as a voltage follower connected operationalamplifier. Here, given that an input voltage at the first input sectionof the second input differential stage circuit section 820 is denoted byVin, and an output voltage at the output section of the first outputdrive stage circuit section 830 is denoted by Vout,Vin=Vout.

Further, the voltage input nodes 825 and 826 in the second inputdifferential stage circuit section 820 are connected with the first andsecond power supply voltages V_(DD) and V_(ML) through the fifth andeighth transfer switch circuit sections SW5 and SW8, respectively.

In the operational amplifier in the second state, simultaneously withthe above, the first input differential stage circuit section 810 andthe second output drive stage circuit section 840 operate as anoperational amplifier. In this case, the signal from the negative DAC istransferred to the odd-numbered output terminal.

First, the signal supplied from the negative DAC (not shown) to thesecond input node 72 of the input switching circuit section 70 istransferred to the first input node 811 of the first input differentialstage circuit section 810 through the twelfth transfer switch circuitsection SW12. At this time, the first and second output nodes 813 and814 of the first input differential stage circuit section 810 areconnected to the first and second input nodes 841 and 842 in the secondoutput drive stage circuit section 840 through the second and thirdtransfer switch circuit sections SW2 and SW3, respectively. Also, atthis time, the output node 843 of the second output drive stage circuitsection 840 is connected to the first output node 903 of the outputswitching circuit section 90 through the fourteenth transfer switchcircuit section SW14.

Also, the output node 843 of the second output drive stage circuitsection 840 is further connected to the second input node 812 of thefirst input differential stage circuit section 810 through the ninthtransfer switch circuit section SW9. Accordingly, the first inputdifferential stage circuit section 810 and the second output drive stagecircuit section 840 operate as a voltage follower connected operationalamplifier. Here, supposing that an input voltage at the first inputsection of the first input differential stage circuit section 810 isdenoted by Vin, and an output voltage at the output section of thesecond output drive stage circuit section 840 is denoted by Vout,Vin=Vout.

Further, the voltage input nodes 815 and 816 in the first inputdifferential stage circuit section 810 are connected with the third andfourth power supply voltages V_(MH) and V_(SS) through the first andfourth transfer switch circuit sections SW1 and SW4, respectively.

In general, in the LCD driving circuit, it is necessary to alternatelyapply positive and negative outputs to the liquid crystal cell toprevent an LCD from being burned. For this purpose, in the case of sucha positive/negative only amplifier configuration, the polarity switchesare required between the output terminal and a drain line of the LCD.For this reason, the cross switch 90 (of the thirteenth and fourteenthswitches SW13 and SW14 in FIG. 4) is inserted between positive andnegative only output stages and the LCD drain line. Further, the inputswitching circuit section 70 is inserted between positive and negativeDAC outputs of a previous stage connected to the operational amplifierand differential stages A 810 and B 820.

As described, when the positive DAC output is supplied to thedifferential stage A/B 810, 820, positive and negative side power supplyvoltages of the differential stage A/B 810, 820 are V_(DD) and V_(ML),respectively. On the other hand, when the negative DAC output issupplied, the positive and negative side power supply voltages of thedifferential stage A/B are V_(MH) and V_(SS) (GND), respectively.

Here, the above-described voltages V_(ML) and V_(MH) are connected incommon, and made equal to the voltage of approximately V_(DD)/2. Thatis, there is an application in which the operation is performed with onepower supply voltage.

The power supply voltage of the two differential stages 810 and 820 arelimited, and therefore input voltage ranges of them are obviouslylimited. By switching the power supply voltages of the differentialstages 810 and 820 based on an input voltage range, a normal operationis consequently performed in the entire input voltage range (V_(SS)(GND) to V_(DD)).

Similarly, the power supply voltages of the two output stages 830 and840 are limited, and therefore output voltage ranges of them areobviously limited. By switching the positive and negative only outputstages based on an output voltage range, an entire output voltage range(V_(SS) (GND) to V_(DD)) can be consequently outputted to anodd-numbered output terminal/even-numbered output terminal.

Here, it should be noted that the voltage of V_(DD)/2 is not necessarilya half of the power supply voltage, but V_(DD)/2±ΔV is also acceptablein terms of an operable range. In addition, typically, ΔV may be arounda few volts.

Next, the operation of the LCD driving circuit according to the presentinvention will be described.

Preferably, the plurality of operational amplifiers that are arranged inparallel in the LCD driving circuit according to the present inventionall operate synchronously. That is, in all of the operationalamplifiers, switching between the first and second operation modes ispreferably made synchronously. For this purpose, preferably, a controlunit (not shown) controls all of the operational amplifiers.

FIGS. 5A and 5B are circuit diagrams showing a configuration of theoperational amplifier circuit section 80 according to the firstembodiment of the present invention. It should be noted that FIGS. 5Aand 5B illustrate one circuit diagram separated into two diagrams.Reference numerals 5 a to 5 j are notations for specifying ten linesdivided between the both diagrams.

The first input differential stage circuit section 810 is provided withfirst and second constant current sources I1 and I2, first to fourthP-channel MOS transistors MP1 to MP4, and first to fourth N-channel MOStransistors MN1 to MN4. The first output drive stage circuit section 830is provided with third and fourth constant current sources I3 and I4,first and second bias voltage sources V_(BP1) and V_(BN1), fifth andsixth P-channel MOS transistors MP5 and MP6, fifth and sixth N-channelMOS transistors MN5 and MN6, first and second resistances R1 and R2, andfirst and second capacitances C1 and C2. The second input differentialstage circuit section 820 is provided with fifth and sixth constantcurrent sources I5 and I6, seventh to tenth P-channel MOS transistorsMP7 to MP10, and seventh to tenth N-channel MOS transistors MN7 to MN10.The second output drive stage circuit section 840 is provided withseventh and eighth constant current sources I7 and I8, third and fourthbias voltage sources V_(BP2) and V_(BN2), eleventh and twelfth P-channelMOS transistors MP11 and MP12, eleventh and twelfth N-channel MOStransistors MN11 and MN12, third and fourth resistances R3 and R4, andthird and fourth capacitances C3 and C4.

In the first input differential stage circuit section 810, one terminalof the first constant current source I1 is connected to the fourth powersupply V_(SS). The other terminal of the first constant current sourceI1 is connected to sources of the first and second N-channel MOStransistors MN1 and MN2. A drain of the first N-channel MOS transistorMN1 is connected to a drain and gate of the first P-channel MOStransistor MP1 and a gate of the second P-channel MOS transistor MP2. Adrain of the second N-channel MOS transistor MN2 is connected to a drainof the second P-channel MOS transistor MP2 and the common terminal ofthe second transfer switch circuit section SW2. Sources of the first andsecond P-channel MOS transistors MP1 and MP2 are connected to the commonterminal of the first transfer switch circuit section SW1. A gate of thefirst N-channel MOS transistor MN1 is connected to a gate of the thirdP-channel MOS transistor MP3 and the second input node 812 of the firstinput differential stage circuit section 810. A gate of the secondN-channel MOS transistor MN2 is connected to a gate of the fourthP-channel MOS transistor MP4 and the first input node 811 of the firstinput differential stage circuit section 810. One terminal of the secondconstant current source I2 is connected to the first power supplyvoltage V_(DD). The other terminal of the second constant current sourceI2 is connected to sources of the third and fourth P-channel MOStransistors MP3 and MP4. A drain of the third P-channel MOS transistorMP3 is connected to a drain and a gate of the third N-channel MOStransistor MN3 and a gate of the fourth N-channel MOS transistor MN4. Adrain of the fourth P-channel MOS transistor MP4 is connected to a drainof the fourth N-channel MOS transistor MN4 and the common terminal ofthe third transfer switch circuit section SW3. Sources of the third andfourth N-channel MOS transistors MN3 and MN4 are connected to the commonterminal of the fourth transfer switch circuit section SW4.

Connection relation between the respective components in the secondinput differential stage circuit section 820 is the same as that of theabove-described first input differential stage circuit section 810, andtherefore detailed description of them is omitted. However, it should benoted that the first to fourth P-channel MOS transistors MP1 to MP4should be replaced by the seventh to tenth P-channel MOS transistors MP7to MP10, the first to fourth N-channel MOS transistors MN1 to MN4 by theseventh to tenth N-channel MOS transistors MN7 to MN10, the first andsecond constant current sources I1 and I2 by the fifth and sixthconstant current sources I5 and I6, the first to fourth transfer switchcircuit sections SW1 to SW4 by the fifth to eighth transfer switchcircuit sections SW5 to SW8, and the points 5 a to 5 j by the points 6 ato 6 j.

In the first output drive stage circuit section 830, the first powersupply voltage V_(DD) is connected to the break terminal of the firsttransfer switch circuit section SW1, the make terminal of the fifthtransfer switch circuit section SW5, a positive side terminal of thefirst constant voltage source V_(BP1), one terminal of the thirdconstant current source I3, and a source of the sixth P-channel MOStransistor MP6. It should be noted that a line representing connectionsbetween the make terminal of the fifth transfer switch circuit sectionSW5 and the other components passes between FIGS. 5A and 5B through thepoint 5 e. The other terminal of the third constant current source I3 isconnected to the break terminal of the second transfer switch SW2, themake terminal of the sixth transfer switch circuit section SW6, a sourceof the fifth P-channel MOS transistor MP5, a drain of the fifthN-channel MOS transistor MN5, one terminal of the first resistance R1,and a gate of the sixth P-channel MOS transistor MP6. It should be notedthat a line representing connections between the make terminal of thesixth transfer switch circuit section SW6 and the other componentspasses between FIGS. 5A and 5B through the point 5 f. A negative sideterminal of the first constant voltage source V_(BP1) is connected to agate of the fifth P-channel MOS transistor MP5. The other terminal ofthe first resistance R1 is connected to one terminal of the firstcapacitance C1. The other terminal of the first capacitance C1 isconnected to one terminal of the second capacitance C2, the output node833 of the first output drive stage circuit section 830, a drain of thesixth P-channel MOS transistor MP6, a drain of the sixth N-channel MOStransistor MN6, the break terminal of the ninth transfer switch circuitsection SW9, and the make terminal of the tenth transfer switch circuitsection SW10. It should be noted that a line representing connectionsbetween the break terminal of the ninth transfer switch circuit sectionSW9 and the other components passes between FIGS. 5A and 5B through thepoint 5 j. Also, a line representing connections between the maketerminal of the tenth transfer switch circuit section SW10 and the othercomponents passes between FIGS. 5A and 5B through the point 5 i. Theother terminal of the second capacitance C2 is connected to one terminalof the second resistance R2. The other terminal of the second resistanceR2 is connected to a gate of the sixth N-channel MOS transistor MN6, asource of the fifth N-channel MOS transistor MN5, one terminal of thefourth constant current source I4, a drain of the fifth P-channel MOStransistor MP5, the break terminal of the third transfer switch circuitsection SW3, and the make terminal of the seventh transfer switchcircuit section SW7. It should be noted that a line representingconnections between the make terminal of the seventh transfer switchcircuit section SW7 and the other components passes between FIGS. 5A and5B through the point 5 a. A gate of the fifth N-channel MOS transistorMN5 is connected to a positive side terminal of the second constantvoltage source V_(BN1). A negative side terminal of the second constantvoltage source V_(BN1) is connected to the other terminal of the fourthconstant current source I4, a source of the sixth N-channel MOStransistor MN6, the second power supply voltage V_(ML), the breakterminal of the fourth transfer switch circuit section SW4, and the maketerminal of the eighth transfer switch circuit section SW8. It should benoted that a line representing connections between the make terminal ofthe eighth transfer switch circuit section SW8 and the other componentspasses between FIGS. 5A and 5B through the point 5 b.

Connection relation between the components in the second output drivestage circuit section 840 is the same as that of the above-describedfirst output drive stage circuit section 830, and therefore detaileddescription of them is omitted. However, it should be noted that thefifth and sixth P-channel MOS transistors MP5 and MP6 should be replacedby the eleventh and twelfth P-channel MOS transistors MP11 and MP12, thefifth and sixth N-channel MOS transistors MN5 and MN6 by the eleventhand twelfth N-channel MOS transistors MN11 and MN12, the third andfourth constant current sources I3 and I4 by the seventh and eighthconstant current sources I7 and I8, the first and second constantvoltage sources V_(BP1) and V_(BN1) by the third and fourth constantvoltage sources V_(BP2) and V_(BN2), the first to fourth transfer switchcircuit sections SW1 to SW4 by the fifth to eighth transfer switchcircuit sections SW5 to SW8, the fifth to eighth transfer switch circuitsections SW5 to SW8 by the first to fourth transfer switch circuitsections SW1 to SW4, the ninth and tenth transfer switch circuitsections SW9 and SW10 by the tenth and ninth transfer switch circuitsections SW10 and SW9, the first and second resistances R1 and R2 by thethird and fourth resistances R3 and R4, the first and secondcapacitances C1 and C2 by the third and fourth capacitances C3 and C4,the points 5 e, 5 f, 5 j, 5 i, 5 a, and 5 b by the points 5 d, 5 c, 5 i,5 j, 5 h, and 5 g.

Referring to FIGS. 5A and 5B, the operation of the operational amplifieraccording to the present embodiment will be described. First, it isassumed that the first input node 811 of the first input differentialstage circuit section 810 is supplied with a positive side voltage in avoltage range of V_(DD)/2 to V_(DD). In this case, states of therespective transfer switch circuit sections SW1 to SW14 are asillustrated in FIGS. 5A and 5B. In this case, a power supply for adifferential pair including the third and fourth P-channel MOStransistors MP3 and MP4 in the first input differential stage circuitsection 810 operates in the range of V_(DD)/2 to V_(DD).

As an output stage for this case, the first output drive stage circuitsection 830 is selected, which is a positive only output stage. That is,the drain of the N-channel MOS transistor MN4, which serves as a singleend output of the above differential pair, and the gate of the N-channelMOS transistor MN6, which is one of inputs of the positive only outputstage, are connected to each other.

In this state, a voltage between the source and drain of the aboveN-channel MOS transistor MN4 corresponds to a voltage between the sourceand gate of the N-channel MOS transistor MN6, and takes a voltage valueof about a threshold voltage, i.e. V_(T)+α. This causes source-drainvoltages of the N-channel MOS transistors MN3 and MN4 constituting anactive load for the above differential pair to be matched, which is agood state in terms of offset voltage. If the negative side power supplyvoltage for the above differential pair is the negative power supplyvoltage V_(SS), i.e., the common terminal of the switch SW4 is connectedto the negative power supply voltage V_(SS), the source-drain voltage ofthe N-channel MOS transistor MN4, which is one of the components of theabove active load, becomes approximately V_(DD)/2+V_(T)+α, so that thesource-drain voltages of the N-channel MOS transistors MN3 and MN4 ofthe active load for the above differential pair are not matched, andtherefore a large offset voltage is generated.

On the other hand, the drain of the second P-channel MOS transistor MP2,which serves as a single end output in a differential pair including thefirst and second N-channel MOS transistors MN1 and MN2, and the gate ofthe sixth P-channel MOS transistor MP6 as a first input node of thefirst output drive stage circuit section, which is the positive onlyoutput stage, are connected to each other. In this state, a voltagebetween the source and the drain of the P-channel MOS transistor MP2corresponds to a voltage between the source and the gate of the abovesixth P-channel MOS transistor MP6, and also takes a voltage value ofapproximately a threshold V_(T)+α.

As a result, source-drain voltages of the first and second P-channel MOStransistors MP1 and MP2 of an active load for the above differentialpair are matched, which is a good state in terms of offset voltage. If apositive side power supply voltage for the above differential pair isconnected through the first transfer switch circuit section SW1 with thepower supply voltage V_(MH) corresponding to approximately a half of thepower supply voltage V_(DD), the P-channel MOS transistors MP1 and MP2of the above active load do not operate. This is because a voltage atthe drain of the second P-channel MOS transistor MP2 becomes higher thana voltage at the source.

In this way, the respective transfer switch circuit sections SW1 to SW14according to the present invention are switched such that all biasstates become best.

Here, an operation of the output stage, i.e., the output drive stagecircuit sections 830 and 840 will be described.

First, the third and fourth constant current sources I3 and I4 areconfigured to have a same current value. This is because the currentflowing through the third constant current source I3 is divided into twoby the fifth P-channel MOS transistor MP5 and fifth N-channel MOStransistor MN5 constituting a floating current source, and a total ofthe two flows through the fourth current source I4 to prevent excesscurrent from flowing through the differential stages 810 and 820.

An operation in floating current sources in FIGS. 5A and 5B will bedescribed. A combination of the fifth N-channel MOS transistor MN5 andthe fifth P-channel MOS transistor MP5 operates as the so-called“floating current source”. In a typical current source includingtransistors, one terminal is connected to a power supply terminal or aGND terminal. However, in the “floating current source”, both terminalsof the current source are in a floating state, and therefore can beconnected to any nodes. The connections of the fifth N-channel MOStransistor MN5 and the fifth P-channel MOS transistor MP5 are locallyapplied with a current feedback of “1”. For this reason, a commonconnecting point between the source of the transistor MN5 and the drainof the transistor MP5 and a common connecting point between the drain ofthe transistor MN5 and the source of the transistor MP5 respectivelyhave high impedances because of the effect of the feedback. It can beseen also from this that the floating current source is configured.

Here, bias design of the floating current source will be described.First, a voltage V_(BN1) between the power supply voltage V_(ML) and abias voltage terminal BN1 is equal to the sum of the gate-source voltageof the sixth N-channel MOS transistors MN6, which is an outputtransistor, and a gate-source voltage of the fifth N-channel MOStransistor MN5. From this, the following equation is met:V _(BN1) =V _(GS(MN5)) +V _(GS(MN6))  (1)where V_(GS(MN5)) is the gate-source voltage of MN5, and V_(GS(MN6)) isthe gate-source voltage of MN6.

In general, a gate-source voltage of an MOS transistor is expressed bythe following equation:V _(GS)=(2I _(D)/β)^(1/2) +V _(TO) +γV _(B) ^(1/2)  (2)whereβ=(W/L)μC _(O)  (2a)γ=((2ε_(O)ε_(S) qN _(A))^(1/2))/C _(O)  (2b)C _(O)=ε_(O)ε_(S) /t _(O)  (2c)Here, W is a gate width, L is a gate length, μ is a mobility, C_(O) is acapacitance per unit area in a gate oxide film, V_(γO) is a threshold atV_(B)=0, V_(B) is a back gate voltage, ε_(O) is a free spacepermittivity (8.86×10⁻¹⁴ F/cm), ε_(S) is a relative permittivity ofsemiconductor (e.g. 3.9), q is an electric charge of an electron(1.6×10⁻¹² coulombs), t_(O) is a gate oxide film thickness, N_(A) is anacceptor density, and γ is a value depending on a process, of which anaverage value is approximately 0.5.

The bias voltage V_(BN1) is determined on the basis of the aboveequations (1) and (2) such that a drain current (I_(D)) has a desiredvalue. In this case, a circuit for generating the bias voltage V_(BN1)typically includes an N-channel MOS transistor to suppress a variationin bias current due to a variation in threshold V_(T) of a transistor.It should be noted that in FIGS. 5A and 5B, the transistor forpreventing the variation is not illustrated.

Regarding the fifth and sixth P-channel MOS transistors MP5 and MP6, thesame bias design can also be applied. Therefore, description thereof isomitted.

Next, a phase compensation will be described. The first and secondcapacitances C1 and C2 and the first and second resistances R1 and R2operate as a phase compensation circuit. Such a phase compensationcircuit is obvious to a person skilled in the art, and not directlyrelated to the present invention, and therefore the description isomitted.

Also, regarding a differential stage B that is the second inputdifferential stage circuit section 820, and a negative only output stagethat is the second output drive stage circuit section 840, as describedabove, switching is made by use of the switches such that a relationbetween a single end output of each differential stage and an input ofeach output stage entirely operate well. Regarding this, the samedescription as in the differential stage A and the positive only outputstage can be applied. Therefore, the description thereof is omitted.

The operational amplifier circuit section 80 according to the presentembodiment is further provided with ninth and tenth transfer switchcircuit sections SW9 and SW10 for voltage follower connections. In theswitch states as shown in FIGS. 5A and 5B, the differential stage A andthe positive only output stage form a voltage follower connection, tooutput a voltage supplied to the differential stage A from an outputterminal Vout of the positive only output stage. Further, thedifferential stage B and the negative only output stage also form avoltage follower connection, to output a voltage supplied to thedifferential stage B from an output terminal Vout of the negative onlyoutput stage.

On the other hand, if the states of the ninth and tenth transfer switchcircuit sections SW9 and SW10 are switched to be brought to statesopposite to the states shown in FIGS. 5A and 5B, the differential stageA and the negative only output stage form a voltage follower connection,to a voltage supplied to the differential stage A from the outputterminal Vout of the negative only output stage. Further, thedifferential stage B and the positive only output stage also form avoltage follower connection, to output a voltage supplied to thedifferential stage B from the output terminal Vout of the positive onlyoutput stage.

It should be noted that the first, fourth, fifth, and eighth transferswitch circuit sections SW1, SW4, SW5, and SW8 operate as switches forpower supply switching, and currents flow through these transfer switchcircuit sections. However, it is in the differential stage that thecurrents flow through the switches. A current in a differential stage ofthe operational amplifier used for a typical LCD driving circuit isapproximately 1 μA, and therefore voltage drops generated due to theswitches are almost negligible. If such switches are inserted for thepower supply voltages in the output stage, a current flowing through theoutput stage is larger by two orders than the current flowing throughthe differential stage, and therefore voltage drops due to the switchesare not negligible. One feature of the operational amplifier circuitsection 80 according to the present invention is in that the voltagedrops due to the currents flowing through the switches are almostnegligible.

FIGS. 7A-1 to 7A-4, and 7B-1 to 7B-4 are circuit diagrams showingconfiguration examples of the transfer switch circuit section used inthe operational amplifier according to the present invention. FIG. 7A-1is a circuit diagram schematically showing a make type switch circuitsection, and FIG. 7A-2 is a circuit diagram showing the make type switchcircuit section with use of an N-channel MOS transistor. FIG. 7A-3 is acircuit diagram showing the make type switch circuit section with use ofa P-channel MOS transistor, and FIG. 7A-4 is a circuit diagram showingthe make type switch circuit section with use of two types of MOStransistors. FIG. 7B-1 is a circuit diagram schematically showing atransfer switch circuit section, and FIG. 7B-2 is a circuit diagramshowing the transfer switch circuit section with use of N-channel MOStransistors. FIG. 7B-3 is a circuit diagram showing the transfer switchcircuit section with use of N-channel MOS transistors, and FIG. 7B-4 isa circuit diagram showing the transfer switch circuit section with useof two types of MOS transistors.

FIGS. 7A-2 and 7A-3 will be described. Both terminals of the make typeswitch respectively correspond to a drain and a source of an N-channelor P-channel MOS transistor. Also, it is assumed that ON/OFF control ofthe switch is performed through a gate. In the case of the N-channel MOStransistor, when the gate is in a high level, the switch is closed,whereas when the gate is in a low level, the switch is turned OFF. Inthe case of the P-channel MOS transistor, the operation is opposite tothe above, in which when the gate is in the low level, the switch isclosed, whereas when the gate is in the high level, the switch is turnedOFF.

FIG. 7A-4 will be described. This switch circuit is provided with anN-channel MOS transistor, a P-channel MOS transistor, and an invertercircuit. The N-channel and P-channel MOS transistors form a combinedcircuit. That is, a drain of the N-channel MOS transistor and a drain ofthe P-channel MOS transistor are connected to each other, and furtherconnected to one terminal of the make type switch. Similarly, a sourceof the N-channel MOS transistor and a source of the P-channel MOStransistor are connected to each other, and further connected to theother terminal of the make type switch. A control terminal of the switchcircuit is connected to an input section of the inverter circuit sectionand a gate of the N-channel MOS transistor. An output section of theinverter circuit section is connected to a gate of the P-channel MOStransistor.

In other words, the switch circuit in FIG. 7A-4 is configured such that,in the N-channel and P-channel MOS transistors combined circuit, therespective drains of the N-channel MOS transistor and the P-channel MOStransistor are connected in common, and the respective sources of theN-channel and the P-channel are connected in common, and the respectivegates are driven by signals having opposite phases with use of theinverter. In this case, when the gate of the N-channel MOS transistor isin the high level, the gate of the P-channel MOS transistor is in thelow level because of the inverter, and both of them are turned ON. Thatis, the switch is turned ON. On the other hand, when the gate of theN-channel MOS transistor is in the low level, the gate of the P-channelis in the high level because of the inverter, and both of them areturned OFF. That is, the switch is turned OFF.

A break type switch can be realized by inversion of control logic of theabove-described make type switch. The same matter as in the make typecan be applied, and therefore description thereof is omitted.

FIG. 7B-2 will be described. This transfer switch circuit section isconfigured such that respective sources of two N-channel MOS transistorsare connected to each other, and the connecting point is used as acommon point. Also, drains of the two N-channel MOS transistors arerespectively used as first and second terminals, i.e., break and maketerminals. Gates of the two N-channel MOS transistors are respectivelyconnected to input and output sections of an inverter circuit section.By connecting a control terminal of the transfer switch circuit sectionto the input section of the inverter circuit section, the two N-channelMOS transistors are supplied with control signals having oppositephases. More detailed operation in each of the two N-channel MOStransistors is the same as that for the case of FIG. 7A-2, and thereforedescription thereof is omitted.

FIG. 7B-3 will be described. This transfer switch circuit section is thesame as that for the case of FIG. 7B-2 except for using two P-channelMOS transistors, and therefore detailed description is omitted. Also,detailed operation in each of the two P-channel MOS transistors is thesame as that for the case of FIG. 7A-3, and therefore descriptionthereof is omitted.

FIG. 7B-4 will be described. This transfer switch circuit section is thesame as that for the case of FIG. 7B-2 or 7B-3, excluding use of twocombined structures each including an N-channel MOS transistor and aP-channel MOS transistor, and therefore detailed description is omitted.

Whether an N-channel MOS transistor, a P-channel MOS transistor, or acombined circuit including an N-channel MOS transistor and a P-channelMOS transistor should be used as the transfer switch circuit sectionused in the operational amplifier according to the present invention,depends on a voltage in each of the transfer switch circuit sections.For example, supposing that a power supply voltage is V_(DD), it ispreferable that, if a voltage applied to a switch is higher thanapproximately V_(DD)/2, the P-channel MOS transistor is used, whereas ifthe voltage applied to the switch is lower than approximately V_(DD)/2,the N-channel MOS transistor is used, and further if it is necessary toperform operation in the entire input voltage range of V_(SS) (GND) toV_(DD), the combined circuit including an N-channel MOS transistor and aP-channel MOS transistor is used.

It should be noted that the switch circuits described in FIGS. 7A-1 to7B-4 are only examples, and a configuration of the present invention isnot limited to any of them.

The differential stage in the conventional example shown in FIG. 2 isprovided with a combination of MN101 and MN102, a combination of MP101and MP102, a combination of MN103 and MN104, a combination of MP103 andMP104, and a combination of MP105 and MP106. In the five combinations oftransistors, a variation in threshold of a transistor affects an offsetvoltage of an amplifier. In the conventional example, as compared with aconfiguration of a typical P/N combined differential stage, the numberof transistors is larger, and consequently the offset voltage is large.Accordingly, if the circuit according to the conventional example isused as the LCD driver, a deviation characteristic may be degraded.

Further, in the conventional example, as can be seen from theconfiguration in FIG. 3, the number of paths that determine a staticcurrent consumption amount is as many as three, even excluding theoutput stage. That is, the three paths are a path through MP107, a paththrough MP108, and a path through MP109. As a result, the conventionalexample has a problem of a large power consumption amount.

Further, referring to FIG. 3, between a drain-source voltage of the PMOStransistor MP109 in the drive stage circuit 130 and a drain-sourcevoltage of a PMOS transistor MP209 in the drive stage circuit 230, thereis a voltage difference of approximately V_(DD)/2. Drain currents of thetwo P-channel MOS transistors MP109 and MP209 represent different valuesdue to the voltage difference and output resistances in pentode regionsof the transistors. That is, the drive stage circuits 130 and 230represent different output characteristics.

Further, an application range of the configuration in the conventionalexample is limited to the circuit illustrated in the conventionalexample, and the configuration cannot be applied to the other typicaloperational amplifier circuit.

According to the operational amplifier and the LCD driving circuit fordriving a liquid crystal display apparatus by use of the operationalamplifier, and the liquid crystal display apparatus according to thepresent embodiment, the problems of the conventional example are allsolved. That is, the number of combinations of transistors having avariation in threshold, which affects an offset voltage of an amplifier,is only four. That is, the four combinations are a combination of MN1and MN2, a combination of MP1 and MP2, a combination of MP3 and MP4, anda combination of MN3 and MN4, which achieve the reduction of onecombination from the five combinations in the conventional example.Thus, the offset voltage can be more improved than that in theconventional example.

Also, in the operational amplifier circuit section 80 according to thepresent embodiment, the number of current paths in the first stage isonly two, i.e., I1 and I2. Further, even in the output stage, the numberof current paths is only two. As described, according to the presentembodiment, a current consumption amount can be made lower than that inthe conventional example.

Also, in the operational amplifier circuit section 80 according to thepresent embodiment, there is no case where a high voltage is applied toa specific transistor to make a circuit asymmetric as in theconventional example.

Further, the present embodiment can be applied to the other circuits,and has advantages that the circuit limitation as in the conventionalexample is absent, and so on.

Second Embodiment

FIGS. 6A and 6B are circuit diagrams showing a configuration of theoperational amplifier circuit section 80 according to a secondembodiment of the present invention. It should be noted that FIGS. 6Aand 6B illustrate one circuit diagram separated into two diagrams.Reference numerals 6 a to 6 j are notations for specifying ten linesdivided between the both diagrams. In addition, an entire configurationof the operational amplifier according to the present embodiment is thesame as that in the first embodiment of the present invention, which isas described with use of the above-described FIG. 4, and thereforefurther description is omitted.

The configuration of the operational amplifier circuit section 80according to the present embodiment is almost the same as that of theoperational amplifier circuit section 80 according to the firstembodiment of the present invention. However, the present embodiment isdifferent from the first embodiment in the following four points. Thatis, in a first input differential stage circuit section 810, oneterminal of the first constant current source I1 is connected to sourcesof third and fourth N-channel MOS transistors MN3 and MN4 and the commonterminal of the fourth transfer switch circuit section SW4, instead ofbeing connected to the fourth power supply voltage V_(SS). Similarly,one terminal of the second constant current source I2 is connected tosources of first and second P-channel MOS transistors MP1 and MP2 andthe common terminal of the first transfer switch circuit section SW1,instead of being connected to the first power supply voltage V_(DD).Also, in a second input differential stage circuit section 820, oneterminal of the fifth constant current source I5 is connected to sourcesof ninth and tenth N-channel MOS transistors MN9 and MN10 and the commonterminal of the eighth transfer switch circuit section SW8, instead ofbeing connected to the fourth power supply voltage V_(SS). Similarly,one terminal of the sixth constant current source I6 is connected torespective sources of seventh and eighth P-channel MOS transistors MP7and MP8 and the common terminal of the fifth transfer switch circuitsection SW5, instead of being connected to the first power supplyvoltage V_(DD).

The configuration of the operational amplifier circuit section 80according to the present embodiment is the same as that in the firstembodiment, except for the above four points, and therefore furtherdescription is omitted.

Referring to FIGS. 6A and 6B, the operation of the operational amplifieraccording to the present embodiment will be described.

A difference between the present embodiment illustrated in FIGS. 6A and6B and the first embodiment illustrates in FIGS. 5A and 5B is in thepower supply voltages applied to a differential pair circuit. That is,in the first embodiment, the voltage applied to the differential paircircuit which includes the first current source I1, the differentialpair transistors MN1/MN2, and the transistors MP1/MP2 serving as theactive load for the differential pair is V_(DD) when the transfer switchcircuit sections are in the first state, or approximately V_(DD)/2 whenthey are in the second state. On the other hand, in the secondembodiment, a voltage applied to a corresponding differential paircircuit is constantly approximately V_(DD)/2.

This leads to a possibility that source-drain voltages of alltransistors to operate are approximately V_(DD)/2 or less. That is,there is an advantage that a required transistor breakdown voltage isonly a half, which then leads to a reduction in cost.

In the above, one of two differential pairs present in the first inputdifferential stage circuit section 810 has been described. However, thesame holds true for the other differential pair (which includes thesecond current source I2, differential pair transistors MP3/MP4, andtransistors MN3/MN4 serving as an active load for the differentialpair). Similarly, the same holds true for two differential pairs presentin the second input differential stage circuit section 820. Detaileddescription of each of them is omitted.

The operation of the operational amplifier in the present embodimentother than the above-mentioned operation is also the same as that in theabove-described first embodiment, and therefore detailed descriptionthereof is omitted.

As has been described above, the operational amplifier of the presentinvention has an advantage of being easily achieved in any type ofoperational amplifier by switching the power supply voltage applied tothe differential stage to match the differential stage to an input levelof the output stage. The conventional example can be realized only withthe specific circuit configuration shown in the conventional example,but cannot be applied in any other circuit (e.g., the operationalamplifier circuit illustrated in the first embodiment).

Since a current flowing through a switch inserted in series in the powersupply for the differential stage is small, and therefore a voltage dropby the switch is small, resulting in small influence on the circuit.

Further, by employing the circuit configuration according to the secondembodiment, a voltage applied to a transistor can be reduced toapproximately a half of the power supply voltage. This results in areduction in breakdown voltage of the transistor, so that a chip sizecan be reduced if the configuration is realized as an LSI. That is, costcan be reduced.

Still further, there is also an advantage that the circuit configurationof the differential stage is a P/N symmetrical configuration, andtherefore an output transient characteristic waveform is alsosymmetrized, so as to meet characteristics required for an LCD sourcedriver.

Yet further, there is an advantage also from the view of a currentconsumption amount that the configuration of the first or secondembodiment has a small number of current paths as compared with theconventional example, and therefore an operational amplifier circuithaving a low current consumption amount can be configured.

The operational amplifier of the present invention is suitable to anoutput amplifier of the LCD driving circuit. In the current situationthat an LCD driving circuit having the outputs exceeding 1000 (channels)is recently developed, a voltage follower connected operationalamplifier is required for the number of channels in the conventionalexample. Accordingly, 1000 times as much as a power consumption amountby one operational amplifier is equivalent to a power consumption amountof one chip. When the number of outputs is large as described, the powerconsumption amount of the chip is increased, and a chip temperature maybe elevated close to 150° C. that is equivalent to a limitation ofsilicon. Even in such a sense, by using the operational amplifier of thepresent invention, the power consumption amount can be reduced.

Although the present invention has been described above in connectionwith several embodiments thereof, it would be apparent to those skilledin the art that those embodiments are provided solely for illustratingthe present invention, and should not be relied upon to construe theappended claims in a limiting sense.

1. An operational amplifier comprising: a control unit configured toswitch an operation mode between first and second operation modes; aninput section configured to receive input signals and supply one of theinput signals as a first input signal to a first input node in saidfirst operation mode and to a second input node in said second operationmode and the other of the input signals as a second input signal to saidfirst input node in said second operation mode and to said second inputnode in said first operation mode; a first differential stage circuitsection configured to differentially-amplify said first input signalsupplied through said first input node in said first operation mode, andsaid second input signal supplied through said first input node in saidsecond operation mode; a second differential stage circuit sectionconfigured to differentially-amplify said second input signal suppliedthrough said second input node in said first operation mode, and saidfirst input signal supplied through said second input node in saidsecond operation mode; a first output drive stage circuit sectionconfigured to amplify said first input signal differentially-amplifiedby said first or second input differential stage circuit section tooutput as a first drive voltage; a second output drive stage circuitsection configured to amplify said second input signaldifferentially-amplified by said first or second input differentialstage circuit section to output as a second drive voltage; an outputsection configured to output through a first output node, said firstdrive voltage in said first operation mode and said second drive voltagein said second operation mode, and to output through a second outputnode, said second drive voltage in said first operation mode and saidfirst drive voltage in said second operation mode; first and secondpower supplies configured to supply voltages in a first voltage range tosaid first differential stage circuit section and said first outputdrive stage circuit section in said first operation mode, and to supplyvoltages in said first voltage range to said second differential stagecircuit section and said first output drive stage circuit section insaid second operation mode; and third and fourth power suppliesconfigured to supply voltages in a second voltage range which isdifferent from said first voltage range, to said second differentialstage circuit section and said second output drive stage circuit sectionin said first operation mode, and to supply voltages in said secondvoltage range in said first differential stage circuit section and saidsecond output drive stage circuit section in said second operation mode,wherein said first or second drive voltage on said first output node isfed back to said first differential stage circuit section from one ofsaid first and second output drive stage circuit sections, and whereinsaid first or second drive voltage on said second output node is fedback to said second differential stage circuit section from the other ofsaid first and said second output drive stage circuit sections.
 2. Theoperational amplifier according to claim 1, further comprising: a firstswitching section configured to switch a connection state of the twosignals to the input nodes of said first and second differential stagecircuit sections in said first and second operation modes; a secondswitching section configured to switch a connection state between saidfirst and second differential stage circuit sections and said first andsecond output drive stage circuit sections in said first and secondoperation modes; a third switching section configured to switch aconnection state between said first and second output drive stagecircuit sections and said first and second output node in said first andsecond operation modes; and a fourth switching section configured toswitch a connection state between said first and second power suppliesand said first and second differential stage circuit sections in saidfirst and second operation modes.
 3. The operational amplifier accordingto claim 1, wherein a voltage of said first power supply is equal to ormore than an upper limit of a range of a voltage outputted from saidoperational amplifier, wherein a voltage of said fourth power supply isequal to or less than a minimum of the range of the voltage outputtedfrom said operational amplifier, and wherein a voltage of each of saidsecond and third power supplies is equal to a voltage between said firstpower supply voltage and said fourth power supply voltage.
 4. Theoperational amplifier according to claim 1, wherein each of said firstand second differential stage circuit sections comprises: a firstdifferential pair having two transistors of a first channel type, andconfigured to input one of said first and second input signals and oneof said first and second drive voltages; a first active load having twotransistors of a second channel type which is opposite to said firstchannel type, and connected with said first differential pair as anactive load and connected with said first and third power supplies; afirst constant current source connected with said first differentialpair; a second differential pair having two transistors of the secondchannel type and configured to input one of said first and second inputsignals and one of said first and second drive voltages; a second activeload having two transistors of said first channel type, and connectedwith said second differential pair as an active load and connected withsaid second and fourth power supplies; and a second constant currentsource connected with said second differential pair.
 5. The operationalamplifier according to claim 4, wherein said first constant currentsource is further connected with said fourth power supply, and whereinsaid second constant current source is further connected with said firstpower supply.
 6. The operational amplifier according to claim 4, whereinsaid first constant current source is further connected with said secondor fourth power supply, and wherein said second constant current sourceis further connected with said first or third power supply.
 7. Theoperational amplifier according to claim 1, wherein the voltage of saidsecond power supply is equal to the voltage of said third power supply.8. The operational amplifier according to claim 1, wherein said firstoutput drive stage circuit section comprises: a first constant currentsource connected between one of outputs of one of said first and seconddifferential stage circuit sections and said first power supply; asecond constant current source connected between the other of theoutputs of the one of said first and second differential stage circuitsections and said second power supply; first and second MOS transistorshaving different channel types and having a source and a drain connectedwith said first and second constant current sources to operate asfloating current sources; a first constant voltage source connected tosaid first constant current source and said first MOS transistor; asecond constant voltage source connected to said second constant currentsource and said second MOS transistor; a third MOS transistor connectedbetween said first power supply and said first output node to operate asan output transistor; a fourth MOS transistor connected between saidfirst output node and said second power supply to operate as an outputtransistor; and a first phase compensation circuit connected betweengates of said third and fourth MOS transistors and connected with saidfirst output node, and wherein said second output drive stage circuitsection comprises: a third constant current source connected between oneof outputs of the other of said first and second differential stagecircuit sections and said third power supply; a fourth constant currentsource connected between the other of the outputs of the other of saidfirst and second differential stage circuit sections and said fourthpower supply; fifth and sixth MOS transistors having different channeltypes and having a source and a drain connected with said third andfourth constant current sources to operate as floating current sources;a third constant voltage source connected to said third constant currentsource and said fifth MOS transistor; a fourth constant voltage sourceconnected between said fourth constant current source and said sixth MOStransistor (MN11); a seventh MOS transistor connected between said thirdpower supply and said second output node to operate as an outputtransistor; an eighth MOS transistor connected between said secondoutput node and said fourth power supply to operate as an outputtransistor; and a second phase compensation circuit connected betweengates of said seventh and eighth MOS transistors and connected with saidsecond output node.
 9. A driving circuit for a liquid crystal displayapparatus, comprising: a plurality of operational amplifiers, whereineach of said plurality of operational amplifiers comprises: a controlunit configured to switch an operation mode between first and secondoperation modes; an input section configured to receive input signalsand supply one of the input signals as a first input signal to a firstinput node in said first operation mode and to a second input node insaid second operation mode and the other of the input signals as asecond input signal to said first input node in said second operationmode and to said second input node in said first operation mode; a firstdifferential stage circuit section configured to differentially-amplifysaid first input signal supplied through said first input node in saidfirst operation mode, and said second input signal supplied through saidfirst input node in said second operation mode; a second differentialstage circuit section configured to differentially-amplify said secondinput signal supplied through said second input node in said firstoperation mode, and said first input signal supplied through said secondinput node in said second operation mode; a first output drive stagecircuit section configured to amplify said first input signaldifferentially-amplified by said first or second input differentialstage circuit section to output as a first drive voltage; a secondoutput drive stage circuit section configured to amplify said secondinput signal differentially-amplified by said first or second inputdifferential stage circuit section to output as a second drive voltage;an output section configured to output through a first output node, saidfirst drive voltage in said first operation mode and said second drivevoltage in said second operation mode, and to output through a secondoutput node, said second drive voltage in said first operation mode andsaid first drive voltage in said second operation mode; first and secondpower supplies configured to supply voltages in a first voltage range tosaid first differential stage circuit section and said first outputdrive stage circuit section in said first operation mode, and to supplyvoltages in said first voltage range to said second differential stagecircuit section and said first output drive stage circuit section insaid second operation mode; and third and fourth power suppliesconfigured to supply voltages in a second voltage range which isdifferent from said first voltage range, to said second differentialstage circuit section and said second output drive stage circuit sectionin said first operation mode, and to supply voltages in said secondvoltage range in said first differential stage circuit section and saidsecond output drive stage circuit section in said second operation mode,wherein said first or second drive voltage on said first output node isfed back to said first differential stage circuit section from one ofsaid first and second output drive stage circuit sections, and whereinsaid first or second drive voltage on said second output node is fedback to said second differential stage circuit section from the other ofsaid first and said second output drive stage circuit sections.
 10. Amethod of an operational amplification, comprising: (a) switching anoperation mode between first and a second operation mode; (b) supplyingvoltages in a first voltage range by first and second power supplies toa first input differential stage circuit section and a first outputdrive stage circuit section, and voltage in a second voltage range,which is different from said first voltage range, by third and fourthpower supplies to a second input differential stage circuit section anda second output drive stage circuit section, in said first operationmode; (c) supplying voltages in said first voltage range to said secondinput differential stage circuit section and said first output drivestage circuit section, and voltages in said second voltage range to saidfirst input differential stage circuit section and said second outputdrive stage circuit section in said second operation mode; (d) inputtingfirst and second input signals; (e) supplying voltages in the firstvoltage range to said first input differential stage circuit section andsaid first output drive stage circuit section, and voltages in saidsecond voltage range to said second input differential stage circuitsection and said second output drive stage circuit section, in saidfirst operation mode; (f) supplying voltages in the first voltage rangeto said second input differential stage circuit section and said firstoutput drive stage circuit section, and voltages in the second voltagerange to said first input differential stage circuit section and saidsecond output drive stage circuit section, in said second operationmode; (g) differentially-amplifying said first input signal by saidfirst input differential stage circuit section, and said second inputsignal by said second input differential stage circuit section, in saidfirst operation mode; (h) differentially-amplifying said second inputsignal by said first input differential stage circuit section and saidfirst input signal by said second input differential stage circuitsection, in said second operation mode; (i) amplifying said first inputsignal differentially-amplified in said (g) or (h), by said first outputdrive stage circuit section; (j) amplifying said second input signaldifferentially-amplified in said (g) or (h), by said second output drivestage circuit section; (k) outputting said first and second drivevoltages obtained in said (i) or (j) from said first and second outputsections in said first operation mode, respectively; (l) outputting saidfirst and second drive voltages obtained in said (i) or (j) from saidsecond and first output sections in said second operation mode,respectively; (m) feeding back one of said first and second drivevoltages outputted from said first output section in said (k) or (l) tosaid first input differential stage circuit section; and (n) feedingback the other of said first and second drive voltages outputted fromsaid second output section in said (k) or (l) to said second inputdifferential stage circuit section.